The present invention relates to a light emitting diode (LED) device in which an LED is mounted as a light source, and more particularly relates to a light correction device.
There has been provided various LEDs which emit the three primary colors, white color, or intermediate colors in recent years, and the LED is used as a light source for the back light of the liquid crystal panel, for various display means such as a keyboard, indicator and others.
FIG. 14 is a sectional view of a conventional LED device. The LED device 110 comprises a substrate 102, connecting electrodes 103 and 104, and an LED 101 mounted on the substrate 102. A cathode 101c of the LED is connected to the electrode 103 with a conductive adhesive, and an anode 101a is connected to the electrode 104 by a wire 106. A protector 107 made of transparent resin is formed on the substrate 102 by molding to seal the LED 101, electrodes 103 and 104, and wire 106.
When an electric current is applied to the LED 101 through the electrodes 103 and 104, the LED emits light. The chromaticity of the emitted light 115 is dependent on the component of the LED. The component of the LED is adjusted so as to obtain desired chromaticity.
However, it is very difficult to manufacture an LED emitting light of desired chromaticity. This is caused by inequality of the wavelength of the emitted light, quantity of fluorescent material in the LED, and others. Such inequality is inevitable.
FIG. 15 is a chromaticity graph showing inequality in white light emitted from LEDs each of which is made so as to emit white light. If the proportion of red (R) is expressed by x, the proportion of green (G) is y, and the proportion of blue (B) is z, white light is as follows.x+y+z=1  (1)
In the graph, sign C0 shows a point where the ratio of R, G, B is 1:1:1 for white chromaticity. In the case, the coordinate is X=0.33, Y=0.33 and Z=0.33. However, actually the chromaticity of white LED is distributed in an area S surrounded by a dot line. An area S0 is practically regarded as a white range. An area S1 is intermediate color range of blue, area S2 is intermediate color of red, area S3 is green, and S4 is magenta.
It is difficult to select the LED included in the area S0 by measuring the chromaticity of a large number of LEDs. As a solution for the difficulty, the following method will be available.                1. Measuring chromaticity of a plurality of LEDs.        2. Classifying the LEDs into the areas S0, S1, S2, S3 and S4.        3. Applying classified LEDs to a field which requires the chromaticity. However, not always all areas are required, resulting in remaining of useless LEDs.        